Active auto focus system improvement

ABSTRACT

An active auto focus system in which a beam of modulated energy is projected towards a subject to be focussed upon with the energy reflected therefrom directed towards a detector array. The detector array comprises a number of radiation responsive elements arranged in parallel rows and in a pattern which permits the reflected energy to impinge upon at least one detector in each of the rows simultaneously. The arrangement allows a digital type output indicative of the position of the reflected energy on the array and thus the position of the subject from the camera.

This is a division of application Ser. No. 129,529, filed Mar. 12, 1980now U.S. Pat. No. 4,317,991 issued Mar. 2, 1982.

BACKGROUND OF THE INVENTION

In recent years a number of auto focus systems particularly for use withcameras have been devised. The majority of such auto focus systems fallinto one of two main types: first the passive type systems wherein twoimages of a scene being viewed are compared with the amount ofdisplacement from a coincidence or superimposed position beingindicative of the range to the subject and second, the active typesystems wherein a projection of either sound or light is directed fromthe camera to the subject and the reflected energy received back isanalyzed to determine the distance to the subject. The present inventionrelates to an active type system which, in the past, have encounteredseveral difficulties.

Active units, using sound as the projection beam, suffer the problems ofreflections off of objects which are not the main subject of the pictureand the inability to focus through a transparent medium such as awindow. Active systems using light or infrared energy heretofore haveusually required moveable projections and/or moveable detectors or haveneeded multiple projectors to establish a focus position. In somesystems, a fixed projector and fixed detectors have been employed butthese systems require specially shaped or masked detectors and/or userather complex electronics to determine the position of the reflectedlight. Furthermore, prior art systems have produced primarily analogoutput signals which are difficult to process and use for positioning acamera lens. While steps have been taken to overcome most of theproblems encountered with prior art systems and accurate in-focuspictures may be obtained in a majority of the cases with either typesystem, a truly simple system having a digital output, having no movingparts other than the camera taking lens, having simple electronics, andhaving a low manufacturing cost has yet to be devised.

SUMMARY OF THE INVENTION

The present invention is an active system utilizing modulated light orinfrared energy and employing a unique detector which works incombination with a lens that, in the preferred embodiment, produces adistorted image of the reflected energy to provide a digital outputsignal indicative of the range to the subject in one of a plurality ofzones. In the present invention, a unique and low cost taking lenspositioning apparatus is utilized which operates from the digital outputwithout the use of servo motors or other high energy consuming andcostly components. More particularly, in the present invention, amodulated source of infrared energy is directed from the camera to thesubject and the modulated reflected energy received from the subject ispassed through a cylindrical lens or other type of distorting lens so asto create an image of the reflected energy which is a narrow strip orline. This line of reflected energy falls upon a novel detector arraywhich is built to have a plurality of separate detector elements in apredetermined pattern thereon. The position of the reflected line ofenergy on the detector is indicative of the distance to the subject andthrough the unique placement of the detector elements on the detectorarray this position is ascertained in a digital fashion with sufficientaccuracy to provide a proper in-focus signal for subjects ranging fromvery near to infinity. A spring biased taking lens is positioned by aplurality of solenoid actuated shims which stop the lens motion at theproper focus zone.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross sectional and partly schematic diagram of thecamera and auto focus circuitry of the present invention;

FIG. 2 shows one embodiment of the detector array with the placement ofindividual detectors thereon;

FIG. 3 is a table showing the zones, the distances involved in eachzone, the system outputs at the various zone positions, the lensextension used for each zone and the nominal position of an in-focussubject in each zone;

FIG. 4 shows an embodiment of the detector array for a four zone system;and

FIG. 5 shows an alternate embodiment of an eight zone system detectorarray.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1, the lens structure of a camera is shown by reference numeral10 comprising a taking lens 12 fastened in a lens mounting 14 which isbiased downwardly by a spring 16. A latch 18 is shown in an indentedportion 20 of the lens mounting 14 and is shown held in this position bya bias member 22 urging the latch member 18 to the left in FIG. 1. Arelease button 26 is shown in FIG. 1 normally biased to the left by aspring member 28 and having a first extension 30 and a second extension34. Upon activation of the release button 26, extension 34 firstoperates to close the switch contacts of an auto focus power switch 32thereby providing power to the system to be described. Further motion ofrelease button 26 causes extension 30 to bear against the latch member18 causing it to move to the right and out of the detent portion 20 andthereby releasing the lens mounting 14 and lens 12 to move downwardly.

When lens mounting 14 and lens 12 move downwardly, an abutment 36 oflens mounting 14 will come in contact with one of a plurality of shimsidentified by reference numerals 40, 42 and 44 depending upon the outputof the auto focus system and will then strike a moveable member 46 whichwill itself move downwardly a small amount indicated by space 48 beforecoming to rest against a fixed member 50. As moveable member 46 movesdownwardly, an extension shown by arrow 52 will operate a switch 54which causes the shutter release mechanism, not shown, to operate. Forpurposes to be explained in greater detail hereinafter, shim members 40,42 and 44 are of different widths and are positioned between theabutment 36 and the movable member 46 in accordance with the actuationof a plurality of solenoids 60, 62 and 64 which are caused to operate bythe output of the auto focus system. Solenoid 60 is shown connected bymeans of a member 66 to shim 40 which is the largest in width, solenoid62 is shown connected by a member 68 to shim 42 which is of the middlethickness of the three shims and solenoid 64 is shown connected by amember 70 to shim 44 which is the smallest of the shims. As can be seen,if none of the solenoids 60, 62, or 64 is actuated, then lens mounting14 will move all the way downwardly until abutment 36 moves member 46into contact with fixed member 50. If solenoid 64 is actuated, thesmallest shim 44 will be placed in between abutment 36 and moveablemember 46 so that the lens mounting 14 will not move as far as it didwith none of the solenoids actuated. In similar fashion, if solenoid 62is actuated, the middle sized shim will be placed between abutment 36and moveable member 46 and again the lens mounting 14 will not movedownwardly as far as it did with solenoid 64 actuated. It can be seenthat by energizing or not energizing one or more of the three solenoids,various combinations of shims may be placed between the abutment 36 andthe moveable member 46 and various amounts of downward motion of lensmounting 14 and lens 12 may be provided. With the use of three solenoidsand three shims, eight different positions of the lens mounting 14 andlens 12 may be obtained. After the shutter release switch 54 hasoperated and the picture has been taken, the film advance mechanism, notshown, will be used to move the lens mounting 14 and lens 12 back to itsoriginal position and latch member 18 will again be moved into theindent 20 so as to hold the lens mounting 14 in the position shown inreadiness for the next picture to be taken.

Also shown in FIG. 1 is a light source 80 identified as LED MOD which,in the preferred embodiment, produces a modulated beam of infraredenergy along the path shown by axis 82 through a lens 84. The modulatedLED 80 may transmit energy in a relatively narrow band preferably in theinfrared region at about 0.94 microns. A filter may also be placed alongaxis 82 to further assure a narrow band of frequency. Lens 84 may act tofocus or collimate the infrared energy directed along axis 82 althoughaccurate collimation is not imperative. The infrared energy travelsalong axis 82 until it strikes a subject whose picture is to be taken.The modulated infrared energy that is reflected back from the subjecttravels along a path shown by axis 86 at the left hand side of FIG. 1and passes through a lens 88 and a distorting lens 90 to thereafterstrike a detector array 92. A filter may also be employed along axis 86to reduce the amount of ambient energy and restrict the frequency thatstrikes detector array 92 to the narrow band projected by the LEDmodulator 80. The distorting lens 90 may be a cylindrical lens mountedas a separate element or may be incorporated as part of lens 88. Otherkinds of lenses which may be made to create a relatively narrow image ondetector array 92 may also be employed and, for example, lens 88 may bemade similar to the astigmatic lenses which are common in the art.

The reflected energy along axis 86 will produce on the detector array 92a relatively thin narrow line image into and out of the plane of FIG. 1and the position of this line will vary with the range to the subject.With the subject at a far distance, axis 86 will be substantiallyparallel with axis 82 and the lens image will strike detector 92 at theright end thereof labeled "∞" in FIG. 1. If the subject were very closeat, for example, one meter, the line image would strike detector 92 atthe left end thereof labelled "1M" in FIG. 1. Positions of the lineimage between one meter and infinity will fall on detector 92 atcorresponding positions between the ends thereof. Detector array 92 iscomposed of a plurality of detectors split into two equal areas andarranged on the surface of the detector in a pattern which will enabledetermination of the position of the reflected energy striking thesurface thereof. FIG. 2 shows one embodiment of the surface of detectorarray 92 in which detectors of various sizes are placed in three rowsthereon. The detectors are preferably photo diodes which generate asignal when energy is imaged on this surface although other types ofdetectors such as photo conducting or even charge coupled devices couldbe employed. The detectors have been shown as rectangles and in practicethis will be their preferred approximate shape although other shapedetectors may also be employed. For convenience, adjacent detectors havebeen shown either dotted or blank for purposes of showing whichdetectors will operate to produce a digital "0" or a digital "1" by thecircuitry to be described. The first row, identified by the letter "A",has a small detector 100 at the left hand side thereof and shown by adotted area. The width of detector 100 is one eighth of the width of thearray and the heighth of the detector 100 may be chosen for convenience.In FIG. 2, detector 100 is shown to be approximately square but theheighth may chosen so as to have a more rectangular shape. Adjacentdetector 100 is a detector 102 which is twice the width of detector 100and is shown blank in FIG. 2. A third detector, 104, is mounted next tothe detector 102 and is of the same width as detector 102 but is shownas a dotted area. A fourth detector, 106, is shown adjacent detector 104and is of the same width as detectors 102 and 104 but again is shown asa blank area. Finally, row "A" contains a fifth detector, 108, at theright hand side which is of the same width as detector 100 and is alsoshown as a dotted area. The second row, identified by the letter "B",has a first detector 110 at the left hand side that is four times thewidth of detector 100 and is shown to be blank in FIG. 2. Row "B" alsocontains a second detector 112 adjacent detector 110, at the right handside of the array, which is of the same width as detector 110 and isshown as a dotted area. The third row, identified by the letter "C", hasa first detector 114 on the left hand side which is of the same width asdetectors 102, 104 and 106 and is shown as a dotted area. Row "C"contains a second detector 116 adjacent detector 114 which is of thesame width as detectors 110 and 112 and is shown in blank area. Finally,row C contains a third detector 118 adjacent detector 116, at the righthand side of the array, which is of the same width as detectors 102,104, 106 and 114 and is shown as a dotted area. Along the bottom portionof FIG. 2, eight divisions or zones, which detector 92 with its arraythereon can detect, are shown and these are identified by the numbers 1through 8. The distorted image of the modulated infrared energy is shownin FIG. 2 as an elongated spot or a thin line image 120 lying in zone 3of the detector array and crossing detectors 106, 112 and 116. Althoughrelatively thin, the width of image 120 is normally much larger than theboundary area between adjacent detectors. The direction of movement ofspot 120, as the object moves, is right and left in FIG. 2 and istransverse to its direction of elongation. The spot has been shownelongated in order to impinge on all three rows of detectorssimultaneously using reasonably large detectors. If very thin rows ofdetectors were used, the spot could be undistorted and still fall on allthree rows simultaneously. As mentioned above, the position of the image120 along the array is indicative of the range to the subject from whichthe energy is being reflected. For example, a subject located quite farfrom the system would cause the line image 120 to be in zone 1 crossingdetectors 108, 112 and 118. As the subject moves closer to the camera,the angle which axis 86 assumes causes the line image 120 to move to theleft in FIG. 1 to a greater and greater extent depending on the distanceto the subject. As a result, the energy shown by the line image 120 inFIG. 2, will move from the right or infinity position through zones 1,2, 3, 4, 5, 6, 7 until finally it arrives at zone 8 at which time theline image 120 would strike detectors 100, 110 and 114.

In FIG. 2, the dotted area detectors 100, 104 and 108 of row A areconnected together to a line not shown in FIG. 2 identified in FIG. 1 asline 130 and the signal thereon is given the designation "a". The blankareas 102 and 106 of row A in FIG. 2 are connected together by a line132 in FIG. 1 and the signal thereon is given the designation "a'". Thedotted detector 112 of row B in FIG. 2 is connected to a line 134 ofFIG. 1 and the signal thereon is given the designation "b". The blankdetector 110 of row B in FIG. 2 is connected to a line 136 in FIG. 1 andthe signal thereon is given the designation "b'". The two dotteddetectors 114 and 118 of row C in FIG. 2 are connected together to aline 138 of FIG. 1 and the signal thereon is designated "c". Finally,the blank detector 116 of row C in FIG. 2 is connected to a line 140 ofFIG. 1 and the signal thereon is designated "c'" . Whenever the lineimage 120 in FIG. 2 strikes the surface of a detector, that detectorwill produce a signal which will be carried by one of the lines 130-140to a signal processing circuit shown in FIG. 1 as the dashed box 150 andwill produce either a digital "0" signal or a digital "1" signaldepending on whether a dotted or blank detector received the image. Itwill be seen from FIG. 2 that if the line of energy 120 is in zone 1,then there will be an output from detectors 108, 112 and 118 and signalswill be produced on lines 130, 134 and 138 which, with the conventionchosen, will produce a "0", "0", "0" output from the circuit to bedescribed hereinafter. With the line image 120 positioned as shown inFIG. 2, detectors 106, 112 and 116 will produce outputs and thesesignals will appear on lines 132, 134 and 140 respectively which, withthe convention used, will produce a "1", "0", "1" output. It will beapparent that as the line image 120 moves to the left in FIG. 2, it willstrike different detectors in different zones and that the combinationof signals for each zone is unique.

The position of the line image 120 on the detector array in FIG. 2, isnot only a function of the range to the subject but also of the detectorlens focal length and the base distance between the two lenses 84 and 88of FIG. 1. The displacement, d, of the line image 120 from the infinityposition may be given by the equation d=fB/R where f is the detectorlens 88 focal length, B is the base distance between lenses 84 and 88and R is the range to the subject. If it is assumed that f is equal to20 millimeters, B is equal to 50 millimeters and R is equal to 1000millimeters at the closest range, the distance d becomes one millimeter.With this combination of values, the total length of the detector arraythen is one millimeter from the infinity edge to the one meter edge. Thewidth of each zone may be calculated from the expression z=fB/R₁ -fB/R₂where z is the zone width, R₁ the near range chosen for the zone and R₂the far range chosen for the zone. Normally the zones are chosen to beof equal width so that lens 12 in FIG. 1 will move substantially equalamounts in changing focus from one range zone to another. Thus, with anarray one millimeter wide, each zone will be substantially one eighthmillimeter and the width of each detector in FIG. 2 is one eighthmillimeter or slightly less due to the width of the border area betweenadjacent detectors. Manufacture of detectors with such small dimensionsis not a difficult problem with today's solid state manufacturingtechniques. Of course other values may be used for desired near range,the base distance and the focal length and the length of the arrayincreased but those chosen above are fairly representative for use on astandard hand held camera. FIG. 2 may be composed of different numbersof rows and different numbers of detectors per row in order to vary thenumber of zones in accordance with the accuracy desired. For example, iffour zone accuracy was all that was necessary, then, as shown in FIG. 4two rows of detectors could be employed and the first row could containa dotted small detector followed by a blank detector of twice the widthas the small detector and followed by a dotted detector of the samewidth as the small detector while the second row could contain a pair ofdetectors each twice as wide as the small detector, one of which wasdotted and one of which was blank. The arrangement of detectors in FIG.2 is established in the preferred embodiment so that as line image 120moves from one zone to another, the output of only one detector at atime changes. This produces an output of a type referred to as "graycode". Obviously, the three rows A, B and C may be placed in differentorder and other arrangements of detectors could be established and stillproduce a gray coded arrangement. For example as is shown from right toleft in FIG. 5, row A might have a small dotted detector, a blankdetector adjacent the small detector but four times as wide and a dotteddetector adjacent the blank detector and three times as wide as thesmall detector while row B might have four detectors alternating dottedand blank with each being twice as wide as the small detector while rowC might have a dotted detector three times as wide as the small detectorfollowed by a blank detector four times as wide as the small detectorand followed by a dotted detector the same width as the small detector.Other arrangements will occur to those skilled in the art. Of course,the detectors might also be arranged to produce a binary output but witha binary code, more than one output can change at the same time. Thegray code of FIG. 2 has the advantage of preventing a significant errorif the width of the line 120 were sufficient to expose two differentdetectors in the same row. Thus, for example, if the line 120 were movedslightly to the left in FIG. 2 and covered both detectors 104 and 106,then with the convention used herein, either a "1", "0", "1" or a "0","0", "1" output might result from the circuitry to be described.Accordingly, the system would respond so as to focus the camera eitherin zone 3 or in zone 4. In either case, it would be quite close to thedesired focus position. On the other hand, if more than one detectorchanged for each of the zones, then the overlapping of two detectors intwo or more rows could result and the system might focus with asignificant error.

For example, in going from a binary 5 to a binary 6, the outputs wouldchange from "1", "0", "1" to "1", "1", "0" in which case an overlappingof the line image might produce a "1", "0", "1", a "1", "1", "0", a "1","1", "1" or a "1", "0", "0", the latter two of which represent a binary7 and binary 4 respectively and the system would not focus in either thezone represented by the binary 5 or the binary 6. In some applications,this might be acceptable but in the present invention, the gray codedarray is preferred. Accordingly, in designing the detector array, it isbest to avoid having two junctures or boundary areas between detectorsin different rows positioned so that the line image can fall on both ofthem and, of course, each of the zones must be unique having a differentarrangement of dotted and blank detectors therein.

Utilizing the equation d=fB/R and the chosen variables for focal length,base, range, and assuming zones of equal width, the distances forsubject range in each of the zones may be calculated. FIG. 3 shows achart in which the eight zones are identified at the top of the columnsand directly below each zone is the distance in meters to the subjectslocated in the far portion of that zone and the near portion of thatzone. For example, in zone 1, the subject may be from infinity to 8meters, in zone 2, the subject may be between 8 meters and 4 meters, inzone 3, the subject may be between 4 meters and 2.66 meters, in zone 4,the subject may be between 2.66 meters and 2.0 meters, in zone 5, thesubject may be between 2.0 meters and 1.6 meters, in zone 6, the subjectmay be between 1.6 meters and 1.33 meters, in zone 7, the subject may bebetween 1.33 meters and 1.14 meters and in zone 8, the subject may bebetween 1.14 and 1.0 meters. In FIG. 3, the outputs of the detectors inrows A, B and C are shown for each of the zones and, as will be furtherdescribed below, it has been assumed that the dotted area detectors ofFIG. 2 produce a "0" signal at the output of the signal processingcircuit 150 while the blank detectors produce a "" signal when the lineimage 120 strikes therein. As can be seen in FIG. 3, the outputs of thethree rows when the energy line is in the first zone will be A=0, B=0and C=0. When the line image 120 is in zone 2 the output will be A=1, B=0 and C=0. In zone 3 the outputs will be A=1, B=0 and C=1. In zone 4the outputs will be A=0, B=0 and C=1. In zone 5 the outputs will be A=0,B=1 and c=1. In zone 6 the outputs will A=1, B=1 and C=1. In zone 7 theoutputs will be A=1, B=1 and C=0. In zone 8 the outputs will be A=0, B=1and C=0. The outputs A, B and C are shown in FIG. 1 as output lines 160,162 and 164 emerging from the signal processing circuit 150 and enteringa converter circuit 166. The purpose of converter circuit 166 is tochange the gray coded signals A, B and C to binary coded signals S, Mand L so as to more easily operate the solenoids 60, 62 and 64, as willbe further explained hereinafter. The converted signals S, M and Lproduced by from converter 166 are shown on output lines 170, 172 and174 of FIG. 1 connected to the solenoids 64, 62 and 60 respectively. The"S" signal on line 170 controls the solenoid 64 operating the small shim44, the "M" signal on line 172 controls the solenoid 62 operating themedium sized shim 42 and the "L" signal on line 174 controls thesolenoid 60 operating the large shim 40.

The converted signals S, M and L are shown in FIG. 3 just below theoutput signals A, B and C and it seen that in zone 1, the convertedsignals are S=0, L=0 and M=0. In zone 2, S=1, L=0 and M=0. In zone 3,S=0, L=0 and M=1. In zone 4, S=1, L=0 and M=1. In zone 5, S=0, L=1 andM=0. In zone 6, S=1, LL=1 and M=0. In zone 7, S=0, L=1 and M=1. In zone8, S=1, L=1 and M=1. As can be seen, the outputs S, L and M are inbinary form and, as such, are most advantageous in performing theoperations of properly energizing solenoids 60, 62 and 64 of FIG. 1.

For each zone detected, the lens 12 will be positioned at apredetermined location with respect to the infinity position. Thepositioning of a 25 millimeter focal length lens for each of the zonesis shown in the fourth row in FIG. 3 and it is seen that in zone 1 thelens extension is 0.04 millimeters from the infinity position. This willproduce an exactly focussed subject at 15.6 meters as is indicated inthe last row of FIG. 3. In zone 2, the lens extension will be 0.12millimeters from the infinity position and this will produce an exactlyfocussed subject located at 5.23 meters. In zone 3, the lens extensionwill be 0.20 millimeters which will produce the exact focus for subjectslocated at 3.14 meters. In zone 4, the lens extension will be 0.28millimeters which will produce an exactly focussed subject at 2.25meters. In zone 5, the lens extension will be 0.36 millimeters whichwill produce an exactly focussed subject at 1.76 meters. In zone 6 thelens extension will be 0.44 millimeters which will produce an exactlyfocussed subject at 1.44 meters. In zone 7 the lens extension will be0.52 millimeters which will produce an exactly focussed subject at 1.23meters. In zone 8, the lens extension will be 0.60 millimeters whichwill produce an exactly focussed subject at 1.06 meters. It is seen thatfor the values chosen, the lens moves 0.08 millimeters for each zonechange. Of course, with the depth of field of the taking lens,satisfactory focus will be obtained for subjects located throughout thezone and usually beyond. It is thus seen that utilizing the eight zonescreated by the arrangement of detectors in FIG. 2, subjects located inany of the eight zones between one meter and infinity can besatisfactorily focussed by use of the present invention.

Referring again to FIG. 1, as mentioned in connection with theexplanation of the detector array of FIG. 2, the signals from thevarious rows of detectors and identified as a, a', b, b', c and c' arepresented on lines 130-140 to the signal processing circuit 150. Morespecifically, the a signal appearing on line 130 is presented through ajunction point 200 to an inverting amplifier 202 which has an output ona line 204. If energy is being received by either detector 100, 104 or108 of FIG. 2, then an "a" signal will appear on line 130 and by virtueof the inverting properties of amplifier 202, the phase of this signalwill be reversed 180 degrees so that the signal appearing on line 204will be 180 degrees out of phase with the signal being emitted from theLED modulator 80. If no energy is being received by either detector 100,104 or 108 of FIG. 2, then there will be no signal on line 130 and nooutput from amplifier 202 on line 204. In similar fashion, if eitherdetectors 102 or 106 are receiving energy in FIG. 2, then an "a'" willappear on line 132 which signal is presented to a noninverting amplifier206 having an output on line 208. The output on line 208 will be asignal in phase with the signal being emitted from LED modulator 80. Onthe other hand, if no energy is being received by either detector 102 or106 in FIG. 2, then there will be no signal on line 132 and there willbe no in phase output signal on line 208. If energy is being received bydetector 112 in FIG. 2, then a "b" signal will appear on line 134 whichis presented through a junction point 210 to an inverting amplifier 212having an output on line 214. Thus, if energy is being received bydetector 112, then a "b" signal will appear on line 134 and by virtue ofthe inverter 212, a 180 degrees out-of-phase signal will appear on line214. On the other hand, if no energy is being received by detector 112,then there will be no signal on lines 134 or 214. If detector 110 isreceiving energy in FIG. 2, then a "b'" signal will appear on line 136which signal is presented to a noninverting amplifier 216 having anoutput on line 218. If detector 110 of FIG. 2 is receiving energy, thenan in-phase signal will appear on line 136 and a similar in-phase signalwill appear on line 218. On the other hand, if detector 110 is notreceiving energy, then no signal will appear on line 136 or on line 218.Similarly, if either detectors 114 and 118 of FIG. 2 are receivingenergy, then a "c" signal will appear on line 138 which signal ispresented through a junction point 220 to an inverting amplifier 222having an output on line 224. Thus, if energy is being received byeither detectors 114 or 118 of FIG. 2, an in-phase signal will appear online 138 and a 180 degree out-of-phase signal will appear on line 224.On the other hand, if no energy is being received by either detectors114 or 118, then there will be no signal on line 138 and on line 224.Finally, if energy is being received by detector 116 of FIG. 2, a "c'"signal will appear on line 140 of FIG. 1 which signal is presented to anoninverting amplifier 226 having an output on line 228. If a signalappears on line 140 indicative of the fact that energy is falling ondetector 116 of FIG. 2, an in-phase signal will appear on line 228. Onthe other hand, if no signal is being received by detector 116 of FIG.2, then no signal will appear on line 140 and on line 228 of FIG. 1.

The signals appearing on lines 204 and 208 of FIG. 1 are presentedthrough resistors 230 and 232 to a junction point 234 connected to anamplifier 236 having an output on a line 238. Resistors 230 and 232 actto sum the signals that may appear on lines 204 and 208. Normally, theline image 120 of FIG. 2 will only fall on a single detector in eachrow, but it may happen that the width of the line image 120 will causeenergy to be received on two adjacent detectors when the line image isclose to the boarder between two adjacent detectors. In the event "a"and "a'" signals may appear simultaneously on lines 130 and 132, anout-of-phase signal on line 204 will occur at the same time an in-phasesignal appears on line 208. However, in all but the rarest of cases,more energy will fall on one detector than the other so that themagnitude of the signal on line 204 will be larger than that on line 208or vice versa. Depending upon which of the signals is largest, anin-phase or 180 degree out-of-phase signal will appear at junction point234 and on the output line 238 of amplifier 236. In similar fashion, theoutput signals on lines 214 and 218 of FIG. 1 are presented throughresistors 240 and 242 to a junction point 244 which is connected to anamplifier 246 having an output on line 248. As with the previouslydescribed summing circuit, under normal conditions there will notsimultaneously be a signal on both lines 214 and 218 but when the lineimage is proximate the junction between detectors 110 and 112 in FIG. 2,energy may fall on both detectors thus producing "b" and "b'" signals atthe same time on lines 134 and 136 in FIG. 1. Because one of thesesignals will almost always be at least slightly larger than the other,the summing resistors 240 and 242 will cause the predominate signal,either in-phase or out-of-phase, to appear at junction point 244 and onthe output line 248 of amplifier 246. Finally, the signals appearing onlines 224 and 228 of FIG. 1 are presented through resistors 250 and 252to a junction point 254 which is connected to the input of an amplifier256 having an output on a line 258. In a manner similar to thatexplained above, there will normally be only one signal either on line224 or on line 228 but when the image line 120 of FIG. 2 is near ajunction point, there may simultaneously be "c" and "c'" signals onlines 138 and 140 of FIG. 1. In either case, any in-phase signalappearing on line 228 will be compared with any 180 degree out-of-phasesignal appearing on line 224 so that the resultant signal appearing atjunction point 254 and on line 258 will be either in-phase orout-of-phase indicative of which of the detectors is receiving all ormore of the energy in row C of FIG. 2. Obviously, the gain of thenoninverting amplifiers 206, 216 and 226, should be the same as the gainof the inverters 202, 212 and 222 and if the gain of the inverters 202,212 and 222 is one, then the noninverting amplifiers 206, 216 and 226may be eliminated.

The signals appearing on lines 238, 248 and 258 in FIG. 1, indicative ofthe detectors which are energized in each of the rows A, B and C of FIG.2 are presented to phase detectors 260, 262 and 264 respectively. Thephase detectors also receive in-phase signals from an oscillator 268 vialines 270, 272 and 274. Phase detectors 260, 262 and 264 compare thephase appearing on lines 238, 248 and 258 respectively with the in-phasesignal from oscillator 268 so as to produce output signals on lines 280,282 and 284 respectively indicative of this phase comparison. The phasedetectors operate to produce a digital "1" signal whenever the inputsthereto are of the same phase, and operate to produce a digital "0"whenever the inputs thereto are of the opposite phase. Morespecifically, if an in-phase signal appears on line 238 indicative ofthe fact that a signal "a'" on line 132 is of predominant magnitude,phase detector 260 will have two in-phase inputs on lines 238 and 274and the output on line 280 will be a "1" whereas if the signal on line238 is 180 degrees out of phase from the signal on line 274 fromoscillator 268 indicative of the fact that an "a" signal on line 130 isof predominant magnitude, the output on line 280 will be a "0". Insimilar fashion, if the signal on line 248 is in-phase with the signalon line 272 from oscillator 268 indicative of the fact that a "b'"signal on line 136 is of predominant magnitude, then a "1" output willappear on line 282 but if the signal on line 248 is 180 degreesout-of-phase with the signal on line 272 from oscillator 268 indicativeof the fact that a "b" signal on line 134 is of predominant magnitude,then a "0" signal will appear on line 282. Finally, if the signal online 258 is in-phase with the signal on line 270 from oscillator 268indicative of the fact that a "c'" signal on line 140 is of predominantmagnitude, then a "1" signal will appear on line 284 but if the signalon line 258 is 180 degrees out-of-phase with the signal on line 270 fromoscillator 268, indicative of the fact that a "c" signal on line 138 isof predominant magnitude, then a "0" signal will appear on line 284. Thesignals on lines 280, 282 and 284 are identified as the outputs A, B andC from the signal processing circuit 150 in FIG. 1 and these signalswill be either "1" or "0" signals depending on the position of lineimage 120 in FIG. 2. Capacitors 290, 292 and 294 are connected betweenthe outputs of phase detectors 260, 262 and 264 and signal groundrespectively so as to smooth the A, B and C signals and reduce noise andalso any ripple that is usually inherent in phase detectors.

Oscillator 268 has an output on a line 296 that is presented throughcapacitors 298, 300 and 302 respectively to lines 130, 134 and 138. Thepurpose of these connections is to produce a slight in-phase signal onlines 130, 134 and 138 respectively so that in the absence of any signalat all from the detectors of FIG. 2, as would occur when the range tothe remote object was quite large, there will be out-of-phase signals onlines 204, 214 and 224 and thus on lines 238, 248 and 258 so that theoutput signals A, B and C will be all "0's" and the apparatus willoperate to focus at infinity or the hyperfocal distance as will befurther explained hereinafter. It should also be noticed that since thebias provided by capacitors 298, 300 and 302 is slightly larger than anynoise expected to be encountered but smaller than the signals from thedetectors, the dotted detectors of FIG. 2 could be eliminated entirelyif desired, since when the line image 120 falls upon an empty spacerather than a dotted detector, the bias produced by capacitors 298, 300and 302 provides a signal to inverters 202, 212 and 222 with the sameresult as if the line image had impinged upon a dotted detector. Inpractice, however, since the production of the detectors is quite easy,it is preferred to have both the blank and the dotted detectors in thearray because it is better to have a well defined signal than the smallbias signal when the energy impinges on a dotted detector. If the biaswere increased to give a larger signal, then with the remote objects,the energy impinging on a detector might decrease below the bias leveland signals from the blank detectors would be overpowered by the biassignal resulting in a false indication.

Oscillator 268 has a final output on a line 304 which is presented tothe LED modulator 80 for purposes of modulating the IR beam eminatingfrom lens 84 and establishing the in-phase signal.

The "A" signal from signal processing circuit 150 appearing on line 160is presented to converter circuit 166 by a line 310 connected to oneinput of an exclusive OR gate 312 which has an output on a line 314identified as the "S" output. The "B" output from signal processingcircuit 150 appearing on line 162 is presented to converter circuit 166through a junction point 320 to a line 322 which is identified as the"L" output. The "C" output from signal processing circuit 150 appearingon line 164 is presented to converter circuit 166 by a line 326 to oneinput of an exclusive OR gate 328 having an output on line 330. Theoutput on line 330 is presented through a junction point 334 to a line336 identified as the "M" output. Junction point 320 is connected by aline 340 to the other input of exclusive OR gate 328 and junction point334 is connected by a line 334 to the other input of exclusive OR gate312. The outputs S, L and M on lines 314, 322 and 336 are connected toconductors 170, 174 and 172 leading to solenoids 64, 60 and 62respectively. The signals S, L and M cause the positioning of small shim44, large shim 44 and medium shim 42 respectively between abutment 36and moveable member 46 for purposes of properly positioning lens 12. Theoutputs S, L and M are also connected by lines 350, 352 and 354respectively to a zone decoder box 356 which may be of the binary tooctal decoder type shown in FIGS. 4-12 of Section 4-8 on page 109 of"Computer Logic Design" by M. Morris Mano published by Prentice-Hall,Inc., Englewood Cliffs, New Jersey. Such a device receives three binarycoded signals and operates to provide eight output signals which areshown in FIG. 1 connected to eight indicating devices identified b yreference numerals 360-367. Zone decoder 356 will analyze the signals onlines 350, 352 and 354 indicative of the S, L and M signals and willproduce indications on indicators 360 through 367 indicative of which ofthe zones 1 through 8 of FIG. 2 the line image 120 impinges upon. Thiswill provide a visual indication to the photographer of what zone thecamera is focussing on.

If the signals A, B and C are all 0, then the exclusive OR gates 312 and328 of converter 166 will operate to produce "0" signals on all threelines 314, 322 and 336 and thus none of the solenoids 60, 62 and 64 willbe activated. This occurs when the energy line 120 of FIG. 2 is in theinfinity position or zone 1 of FIG. 2. As a result, when the latchmember 118 releases the lens mounting 14, abutment 36 will move downuntil it contacts moveable member 46 and both lens mounting 14 andmoveable member 46 will move a distance equal to the spacing 48 beforecoming to rest. The length of member 46 is chosen to provide the lensextension necessary for the zone 1 which is 0.04 millimeters and is thehyperfocal position. Thus when the lens 12 comes to rest and shutterrelease switch 54 is actuated, the lens will be in the proper positionfor subjects located between 8 meters and infinity from the camera. Ofcourse, member 46 could be firmly mounted against the fixed member 50but then alternate arrangements would have to be used to actuate switch54.

In zone 2 when the output A is a "1", the output B is a "0" and theoutput C is a "1", the exclusive OR gates 312 and 328 will operate sothat the output S is a "1", the output L is a "0" and the output M is a"0". Under these circumstances, a signal will appear on line 170 but noton lines 172 and 174 and solenoid 64 alone will be actuated so as toinsert shim 44 between abutment 36 and moveable member 46. Shim 44 ischosen to have a width of 0.08 millimeters and accordingly, when latchmember 18 releases lens mounting 14, abutment 36 will move until itcontacts shim 44 and together they will move until they contact moveablemember 46 and an additional amount of movement will be allowed due tothe spacing 48. As a result, the lens mounting will come to rest at aposition which is the sum of 0.04 millimeters representing thehyperfocal position and the 0.08 millimeter width of shim 44. The lenshousing will therefore stop in a position which is 0.12 millimeters fromthe infinity position which, as seen in FIG. 3, is the zone 2 lensextension position and subjects between 8 meters and 4 meters from thecamera will be properly focussed. In zone 3, the outputs A, B and C are1, 0 and 1 respectively and the exclusive OR circuits 312 and 328operate to produce the signals S=0, L=0 and M=1. As a result, solenoid62 will be actuated and shim 42 will be moved in between abutment 36 andmoveable member 46. Shim 42 is chosen to have a width of 0.16millimeters and accordingly, when latch member 18 releases lens mounting14, abutment 36 will move down until it contacts shim 42 and theytogether will move until they contact moveable member 46 and all threewill move the distance provided by space 48 at which time the shutterrelease mechanism 54 is actuated. In this position, the lens mounting islocated the sum of 0.04 millimeters+0.16 millimeters=0.2 millimeterswhich is the proper setting for zone 3 and subjects between 4 meters and2.66 meters will be properly focussed. In zone 4, the outputs A, B and Care "0", "0" and "1" respectively and the exclusive OR gates 312 and 338operate to produce the signals S=1, L=0 and M=1 for zone 4. As a result,solenoid 64 and 62 will be actuated and the small and medium shims 44and 42 respectively will both be inserted between the abutment 36 andthe moveable member 46. As a result, when the lens mounting comes torest, its position will be the sum of 0.04 millimeters, shim 44's widthand shim 42's width which totals 0.28 millimeters and is the correctposition for zone 4 so that subjects between 2.66 meters and 2 meterswill be properly focussed. In zone 5, the A, B and C outputs are "0","1" and "1" and the converted outputs S, L and M become "0" , "1" and"0" respectively. Under these circumstances, solenoid 60 is actuated andlarge shim 40 is inserted between abutment 36 and moveable member 46.Shim 40 has a width of 0.32 millimeters and as a result, the lensmounting 14 will come to a rest position representing the sum of thewidth of shim 40 and 0.04 millimeters, the total of which is 0.36millimeters. This is the correct position for zone 5 and subjectsbetween 2 meters and 1.6 meters will be properly focussed. In zone 6,the A, B and C signals each become "1's" and the converted signals S, Land M become "1", "1" and "0" respectively. Under these circumstancessolenoids 60 and 64 will be actuated inserting shims 40 and 44 betweenabutment 36 and moveable member 46. The lens mounting 14 will thereforecome to a rest position which is 0.44 millimeters from the infinityposition and subjects between 1.6 meters and 1.33 meters will be infocus. In zone 7, the outputs A, B and C are "1", "1" and "0"respectively and the outputs of the conversion circuit 166 become S=0,L=1 and M=1. Under these circumstances, solenoids 60 and 62 will beactuated and shims 40 and 42 will be inserted between abutment 36 andmoveable member 46. The lens mounting will therefore come to a restposition at 0.52 millimeters from the infinity position and subjectsbetween 1.33 meters and 1.14 meters will be in focus. Finally, in zone 8the outputs A, B and C are 0, 1, 0 respectively and the convertedoutputs S, L and M become 1, 1 and 1 respectively. Under thesecircumstances, all of the solenoids 60, 62 and 64 will be actuated andall of the shims 40, 42 and 44 will be inserted between abutment 36 andmoveable member 46. Thus, when the lens mounting 14 comes to rest, itwill be in a position representative of the sums of the thicknesses ofthe shims plus 0.04 millimeters. This sum is 0.60 millimeters, thecorrect distance for the lens extension in zone 8 and subjects between1.14 meters and 1 meter will be properly focussed.

It is thus seen that I have provided an active auto focus systememploying a novel detector which can determine in which of 8 zones alight image is present with each of the zones representing a differentrange from the camera to the subject. It is seen that my system is notcomplex and may be easily and inexpensively produced. It is also seenthat I have provided a novel, accurate and inexpensive arrangement formoving the lens to the correct focus position without the use ofelectrical motors. Many obvious alterations will occur to those skilledin the art and I do not wish to be limited by the specific disclosuresused in connection with the preferred embodiment. I intend only to belimited by the following claims.

The embodiments of the invention in which an exclusive property or rightis claimed are defined as follows:
 1. Apparatus for positioning thetaking lens means of a camera comprising:housing means carrying the lensmeans and movable along a first path; a first member positioned apredetermined space from the housing means in the first path, thehousing means moving in the first path, contacting the first member andbeing restrained from further movement in a first position after thehousing means has contacted the first member; and spacing means operableto move into and out of the predetermined space and operable when in thepredetermined space to cause the housing means in its movement in thepath to contact the spacing means, said housing means and said spacingmeans thereafter moving together in the first path, contacting the firstmember and being restrained from further movement with the housing meansin a position other than the first position after the housing meanstogether with the spacing means has contacted the first member. 2.Apparatus according to claim 1 wherein the spacing means comprises afirst shim having a first width and a second shim having a second width,each shim being independently operable to move into the predeterminedspace and wherein with no shim in the predetermined space the firstposition is such that the lens means provides a satisfactory focus atthe image plane thereof for objects located in a first zone of rangesfrom the camera, with the first shim in the predetermined space, thehousing means is restrained at a second position such that the lensmeans produces a satisfactory focus at the image plane thereof forobjects located in a second zone of ranges from the camera, with thesecond shim in the predetermined space, the housing means is restrainedat a third position such that the lens means produces a satisfactoryfocus at the image plane thereof for objects located in a third zone ofranges from the camera, and with the first and second shims in thepredetermined space, the housing means is restrained at a fourthposition such that the lens means produces a satisfactory focus at theimage plane thereof for objects located in a fourth zone of ranges fromthe camera.
 3. Apparatus according to claim 1 further including a thirdshim having a third width and movable into the predetermined zoneindependently of the first and second shims is included and the housingmeans is restrained in fifth, sixth, seventh or eighth positions by themoving of the third shim alone or in combination with the first andsecond shims into the predetermined space.